SA519401518B1 - Quench Column Aftercooler - Google Patents

Abstract

A process for cooling quench effluent includes providing a quench column (10) effluent to a quench column aftercooler condensate (85); cooling the quench column effluent to provide a quench column aftercooler condensate (85); and recirculating at least a portion of the quench column aftercooler condensate (85) to the quench column aftercooler at a rate to prevent fouling of the quench column aftercooler (10). Fig 1.

Description

Quench Column Aftercooler FULL DESCRIPTION BACKGROUND OF THE INVENTION A coin is provided to cool the 000179 quench column flow in the eg .quench column aftercooler more specifically; The process involves recirculating a minimum of ga of condensate to the abolition column aftercooler to the abolition column aftercooler. Various processes and systems for the manufacture of acrylonitrile and methacrylonitrile are known; See, for example, US Patent No. 9 and typically; The process of recovering and purifying the acrylonitrile / methacrylonitrile produced by the direct reaction of hydrocarbon selected from the group consisting of oe 0 propane, propylene, isobutylene, ammonia 28 and oxygen 00 in the presence of a catalyst was achieved by transferring The reactor effluent containing acrylonitrile/metacarbonitrile to the Jol column (quenching) where the reactor effluent is cooled with a water stream first” and the coolant effluent containing acrylonitrile/metacarbonitrile is transferred to the column Of an absorber where the cooled impurities are connected to a water stream gb for adsorption of 5 acrylonitrile/metacarbonitrile in the second water stream; Transferring the second water stream containing acrylonitrile/metacarbonitrile from the second column to a distillation column, the first recovery column, to separate the crude acrylonitrile/metacarbonitrile from the second water stream, and transferring the separated acrylonitrile/metacarbonitrile to a distillation column, a second column. heads column to remove at least some impurities from the crude acrylonitrile/metacrylonitrile 0 and transfer the partially purified acrylonitrile/methacrylonitrile to a third distillation column (production column) to obtain the acrylonitrile/methacrylonitrile product. Patents explain

American numbers 44,234,510 5¢ 3,936,360 and 3,885,928; and 3,352,7164; and 3,198,150 and 3,044,966 modulation recovery and acrylonitrile/methacrylonitrile purification processes. The effluent from the quench column can also be cooled before being transported to other dimensional equipment. on one side; The stream was cooled by quench in an indirect contact cooler; It is called a quench aftercooler (QAC) before moving to the absorber column The quench aftercooler is a vertical shell-tubular heat exchanger with the feature of process flow through the tube side and coolant at the shell side. The effluent vapor is cooled as it passes through the tubes and some of the organic material is essentially evaporated; acrylonitrile 0 and water; This is called Bale intensification of the process. The non-condensing vapor exits from the bottom of the abatement aftercooler through a nozzle inside the exchanger under the tubular casing. Process condensate exits from the bottom of the quenching aftercooler under control and is pumped to the dimensional equipment absorber or recovery column The process may encounter clogged aftercooler piping which requires periodic shutdown 5 of the facility for mechanical cleaning for aftercooler quenching. The blockage is due to the gradual accumulation of polymer in the daly tubes. The polymer is mainly polyacrylonitrile - NO 0M 06 2. The reason for the polymerization is that some of the acrylonitrile materials evaporate in the tubes and this acrylonitrile monomer is not inhibited, which actually allows polymerization to occur. In addition to that; The quench stream contains some ammonia that is not removed in the quenching. The ammonia reacts with 0 acrylonitrile in the fluid phase condensate to form the polymer pOlYMEr. The acrylonitrile polymer is viscous and can adhere to the walls of the inner tubes and gradually build up, causing blockage of the tubes. tubes General description of the invention

The suppression flow cooling process includes cooling the quench column stream to provide an intense sale of the suppression column aftercooler; and recycle at least a portion of the bulking material of the abolition column aftercooler to the abolition column aftercooler. The process provides a tube-side scalding factor of 0.0006 m2 (°C) per kcal/hr or less in the quenching column aftercooler and a heat transfer coefficient of up to 270 kcal/hr per m2 (degrees (sie) more). The process includes flow cooling Amortization involves providing an abolition column flow of condensate to the abolition column aftercooler; cooling the abolition column flow to deliver condensate to the abolition column aftercooler; and recirculating at least a portion of the abolition column aftercooler condensate to the abolition column aftercooler at a rate to prevent fouling of the aftercooler for the quenching column.

0 quench flow cooling process; Where the process includes supplying an abatement column flow to the abolition column aftercooler; and cooling of the suppression column flow to deliver condensate to the aftercooler of the suppression column; and recycle at least a portion of the abolition column aftercooler condensate to the abolition column aftercooler at some rate to provide a fluid film of about 0.1 to 1.1 mm thickness in the heat exchanger tubes at the abolition column aftercooler dirt inlet.

5 The suppression flow cooling process includes supplying a suppression column flow to a suppression column aftercooler; determination of ammonia concentration in the quenching column stream; and recycle at least a portion of the abolition column cooler condensate to the abolition column aftercooler when the ammonia concentration in the abolition column cooler reaches about 20 ppm (by weight) or more. The suppression flow cooling process includes supplying a suppression column flow to a suppression column aftercooler; and specify

0 acrylonitrile concentration in the quenching column stream; and recirculation of at least a portion of the AEC material of the abolition column cooler to the abolition column aftercooler when the concentration of acrylonitrile in the abolition column stream reaches about 969 wt. or more. The suppression stream cooling process includes providing a suppression column flow to a dled column aftercooler] where the suppression column stream comprises about 20 ppm (by weight) or AST of ammonia and/or about 969

by weight or more acrylonitrile; and recirculation of at least part of the condensate of an abolition column aftercooler to the abolition column aftercooler. BRIEF EXPLANATION OF DRAWINGS The above aspects, features and other advantages of the various aspects of the process will be more clearly visible through the following figures. Figure 1 shows in general a quenching column and aftercooler. Figure 2 shows the upper tubular shell of the quenching aftercooler. Like-reference symbols indicate similar components across the many projections of shapes. Those with experience in the art will recognize that the elements in the figures are illustrated for simplicity and clarity 0 and are not necessarily scale specific. For example; Some objects in the figures can be exaggerated relative to objects (GAY) to help improve understanding of various aspects. In addition to that; The general and well-understood elements useful or necessary for a commercially viable aspect are not usually spelled out to facilitate a less objectionable view of these several aspects. Detailed Description: 5 1 The following description is not a limitation, but is intended solely for the purpose of describing the general principles of the illustrative d models. The detection range shall be specified with reference to the protections. Quenching column and aftercooler for damping column and as shown in Fig. 1; The quench column 10 includes a first segment 28, a second segment 30, and the first segment 28 is located below the second segment 30. The first segment 28 of the quench column 0 10 includes a Lge 32 inlet for receiving a gaseous stream or reactor effluent 12. It can include The gaseous stream or reactor stream 12 contains acrylonitrile and ammonia . The second part 30 of the quenching column 10 includes a multi-level spray system 34 Lge to receive

Waterstream or Quenching Fluid 16. Waterstream or Quenching Fluid 16 may include an acid

.6

Quench fluid 16 may comprise the bottom stream of the quench column or

The stream exits from the lower part 42 of the damping shaft 10 and crosses the line 44. On one side; The bottom stream of the atomization column or effluent may include an ammonium sulfate concentrate

9625 On the other hand; About 10 to “J up to about 1645 wt. or Cunsulfate

By weight Ag another side is about 15 to 9621 by weight.

Water can be added via line 46 to quench column 10 via inlet 49 or rather water can be added

Suppression fluid 16 or elsewhere in the fluid recirculation cycle formed by the two streams 16

0 and 44. Mah can also be added to the quench column 10 via some line 68. In this aspect; The quenching column may be of any type of quenching column known in the art; The quenching column may include packing or trays. (Sa) Recirculation of the aqueous fluid 16 through a line 44 and returns to the aeration column using a pump Ma 50. In this aspect, the amortization column can have multiple return lines. It is possible to pull

5 Outlet stream 67 As part of the underparts stream of the quenching shaft that exits through a line 44 to maintain a constant mass flow Gas in the sale cycle) Circulate the liquid by displacing the added liquid. Exit stream 67 removes neutralization reaction products formed such as ammonium sulfate (JU) and is also useful for preventing concentration of unwanted products in the liquid recirculation cycle; Jie corrosion products. Exit stream 67 can be withdrawn from the line 44 at the point dump

0 is S2 on one side; Each dash 47 of the spray system 34 can be configured to spray downward using a hollow aerosol spray for the aqueous fluid 16) where each spray locates a hollow cone Ie equidistant from the walls of the hollow cone spray. On one side, the nozzles of each spray bar can be spaced so that The gia consists of a hollow cone first spraying the alkali liquid from a rod first nozzle

A first spray overlaps with a second hollow cone spray part of the quenching liquid from a second nozzle of the first spray applicator to provide an overlap of the quenching liquid. In another aspect the suppression column can include packed sections of multiple sheets instead of the multi-level spray system 34. In this aspect; The damping fluid 16 is circulated to the damping shaft above and/or below the padded section or plate of the shaft.

The refrigerant effluent gas containing acrylonitrile including co-products such as acetonitrile, hydrogen cyanide, ammonia 08 and other impurities as well as mist can arise from the multi-level spray system 34 of the desiccant mist eliminator 26. Jie

0 MIST 26 To remove mist from the refrigerant flue gas. The mist eliminator 26 is located after the second part 30 of the damping column 10. The mist eliminator 26 may incorporate a water mist system (not shown). The water spray system is configured to spray water onto one surface of the mist eliminator 26; As droplet aggregation is reduced and polymer formation and related fouling are reduced on the mist eliminator surfaces 26. The damper or coolant incorporating acrylonitrile including products can exit the stream

5 Common Jie acetonitrile, hydrogen cyanide, ammonia and other impurities); After passing through the deodorizer 26; of quenching column 10 HS Gazi 70. On one side; The quenching column stream is the gas stream 70. The gas stream 70 may be sent to one or more withdrawn material sorters 82 and one or more aftercoolers of the quenching column 80. The process may include the use of aftercoolers

For quenching column JB such as shell, tube, fin tube, box type, plate type, helical type and double tube type. Condensate 85 can be removed from quenching column after cooler 80 at outlet 90. The process also includes transfer of sale Condensate 85 via pump 95 back to the quenching column aftercooler 80. Eda from condensate 85 can be sent to dimensional equipment (fie absorber and recovery column (not shown). The number is measured

The pH of the condensate is 85 before entering the dimensional equipment. The process stream 110 is a vapor stream from the aftercooler 80 that can be forwarded to an absorber. Operation without recirculation Figure 2 is an upper-perspective projection of the inlet tubular casing 18 located in an abatement column aftercooler. The inlet tubular casing 18 may include the inlet group of tubes 24. The abatement column flow condenses and serves as condensate for an abolition column aftercooler. The quenching column effluent vapor may include acrylonitrile with co-products and impurities. in this aspect; The quenching column effluent vapor may contain acrylonitrile, hydrogen cyanide, ammonia and other impurities. In this side 0 the vapor stream of the quenching column is between about 9 and 9613 wt acrylonitrile and in the AT side it is about 11 and 9612 wt acrylonitrile. Wad quenching column effluent vapor may contain about 1.0 and 961.5 by weight of hydrogen cyanide and about 5 and 200 ppm (by weight) of ammonia. The amortization column aftercooler thickener mainly comprises water and acrylonitrile with smaller amounts of other components such as acrylonitrile, hydrogen cyanide 5 and acrylic acid. Since the steam of the atomizing column stream initially enters the tubular jacket 18 through the tube inlets 24 the surfaces of the cooling tubes are continuously moistened with the first drops of the condensed vapor. Because OY the first liquid droplets continue to flow down through the tubes; The wetted pipe surface area can automatically become dry until additional condensation occurs in this area from the continuous flow of steam of the quenching column stream. Continuous wetting and drying enables gradual deposition of the polymer onto the surfaces of the cooling tubes. In this aspect, some polymerization occurs in the form of liquid droplets and some solid polymers remain on the surface of the coolant tube when the surface of this wet coolant tube dries. The quench flow at the inlets of the refrigerant tube will have a temperature between 60 and 90°C.

An increase in droplet formation and size and a decrease in tube surface dryness also occur below the refrigerant tube surface as the distance from the tube inlet 24 increases. As the distance from the tube inlet 24 continues to increase; Sufficient condensation and droplet formation occurs so that the liquid flows down the refrigerant tube wall and the wall is mainly covered by a liquid film. In this regard; The polymer is continuously washed off the surface of the coolant tube resulting in minimal solid polymer build-up on the wall of the coolant tube. Also for clarity it has been shown that to operate the aftercooler without rotating Bale; The thickness of the liquid film at the top of the tubes is essentially zero; As there is almost no condensation at all. in the middle of the tubes; The thickness of the liquid film is in the order of 0.1 to 0.15 mm. and in (Sal) the lower 0 of the tubes; The thickness of the liquid film is in the order of 0.25 to 0.3 mm. In addition to that; Dirt in the aftercooler has been shown to occur in the upper half of the tubes; With very little dirt in the bottom half of the tubes. Operation With Recirculation to one side; The abolition column aftercooler ha condensate is recycled to the abolition column aftercooler 5. Fig. 2 Ble of top view projection of the tubular inlet 18 aftercooler of an abatement column. The inlet casing 18 may include a set of tube inlets 4. The liquid covers the top of the casing 18 and flows into the inlets of the casing 24 and flows down into the refrigerant tubes. The tubular casing 18 and the refrigerant piping are mainly wetted at the inlet of the tubular casing 24 and in the refrigerant piping. Condensation occurs when the stream vapor flows down the tube. The thickness of the liquid film on the surface of the refrigerant tube increases as the distance from the tubular casing inlet increases 24. Base wettability of the entire surface of the refrigerant tubes allows continuous washing of the surface of the refrigerant tube and minimal build-up of solid polymer on the surface of the refrigerant tubes. In another aspect the process involves [sale] recirculating not less than a portion of the abolition column aftercooler condensate to the abolition column aftercooler at some rate to prevent fouling

Quenching column aftercooler. in this aspect; The abolition column aftercooler condensate is recycled to the abolition column aftercooler in the recycling process or a recirculation rate of about 0.3 to 10; on the pal side between about 0.3 and 3; And on the other side between about 1 and 3 and on the other side between about 0.3 and 1. As used here "recycle rate" or "ale ratio" means the molar flow rate of recirculating liquid 85 divided by the flow rate

molarity of abatement effluent vapor 70. The process provides a tube-side smut factor of 0.0006 m2 (°C) per kcal/hour or less in the abatement column aftercooler; On the other side about 0.0005 m2 (Asie degree) per kcal/hour or less; Ag on the AT side about 0.0004 m2 (degrees

(Lge 0 per kcal/hour or less. The process provides a rate of change of the tube-side dirt coefficient in the abolition column aftercooler of approximately 0.00002 m2 (°C) per kcal/hour/month or less. lg, of the process; Controls recycling rates and soiling coefficient to provide a heat transfer coefficient of about 270 kcal/hr per m2 (°C); on the other hand, about 278 kcal

5 kcal/h per m2 (Augie degree or more) Ag other side about 285 kcal/h per m2 (°C) or more. The process provides a rate of change in heat transfer coefficient of up to 5 kcal/h per m2 (degrees sie/month or less. On the AT ¢ sale side) the abolition column aftercooler is circulated to the abolition column aftercooler at a rate to provide and maintain a liquid film over the entire surface of the piping. On this side; Done

sale) 0 Circulation of the abolition column aftercooler condensate to the abolition column aftercooler at some rate to provide a liquid film thickness at the top of the tubes from about 0.1 to 0.15 mm up to about 1.0 and 1.1 mm in the heat exchanger tubes (at the tube inlet ) in the aftercooler of the quenching column and on the other side from about 0.1 and 0.15 mm up to about 0.45 and 0.5 mm and on the other side at about 0.1 and 0.15 mm up to about 0.2 and 0.25 mm.

— 1 1 — The thickness of the liquid film was estimated based on the tube flow rates of the liquid and gas with the fluid isolated from the annular region at the tube wall and the gas flow through the turbulent core. The fluid shear stress and viscosity in the annular region of the laminar flow were calculated using links provided by Bird and Stewart [1190100]. The gas phase shear stress was calculated using the Blasius equation. The membrane potential was found by equating the liquid, vapor viscosity, and shear stress at a surface

liquid and gas. As shown in the following calculated values (assuming clean feeding without soiling); Where the rate of recycling (sale) and the thickness of the film increase and decreases the heat transfer coefficient .coefficient.

Film thickness (mm) | Shall transfer coefficient

(kcal/hour per m2 degrees Celsius)

0 . | | | a a ’ i i ’ as shown in the following calculated values (assuming normal feeding with dirt) and the higher the sale rate, the lower the dirt factor. The heat transfer coefficient increases at recirculation (sale) rates ranging from 0.1 to 3 compared to the recirculation rate of 0. The effect of recirculation rate on the inlet temperature of the quenching column is shown.

— 2 1 — Tubular side of heat transfer factor coefficient 1 Filth factor inlet temperature + recirculation rate (kcal/hr clinging side per m2°C) of fouling factor A 'a . 7 a. - - - - In this aspect provides a recirculation rate of about 1 0 to 1, a fouling coefficient of about 0.0012 to 0.0004 m2 (°C) per kcal/hour and a heat transfer coefficient of about 300 to 400/kcal/hour per m2 (°C). On the other hand, it provides a recirculation rate of about 0.3 to 1, a fouling factor of about 0.0004 m2 (degrees degress) per kcal/hour and a heat transfer coefficient of between 390 and 350 kcal/hour per m2 (°C). on one side; The process includes recirculation of at least a portion of the abolition column aftercooler condensate to the abolition column aftercooler when the ammonia concentration in the abolition column aftercooler is about 20 ppm (by weight) or more; On the other side it's about 50 ppm 0 (by weight) or ST and on the other side it's about 100 ppm (by weight) or more. in a relevant aspect; The process includes recirculation of at least a portion of the abolition column aftercooler condensate to the abolition column aftercooler when the concentration of acrylonitrile is in the column stream

— 3 1 — Quenching about 969 wt. or more on the other side about 9610 wt. or more and on the other side about 9611 wt. or more. in this aspect; The process can include adjusting the cycle sale rate based on the concentration of ammonia and/or acrylonitrile in the quenching column stream. Recycle rates can be set based on the ammonia concentration in the quenching column stream as shown below. Ammonia Concentration in Suppression Column Stream Recycling Rate 0 and 100 ppm (by weight) 1.03 Greater than 100 ppm (by weight) 0 and 3.0 Spraying of the Tube Sheet on one side; The process includes supplying condensate to the aftercooler of the tubular casing amortization column. The process can include the provision of a condensed sale of aftercooler to a tubular casing abolition column with or without the use of a spray nozzle. The process is most effective in reducing fouling when the 0 jacket 1 tubes in the abolition column aftercooler are completely covered by spraying the abolition column aftercooler condensate. In this side; The abolition column aftercooler condensate can be transferred to the tubular casing using one or more Jie AD nozzles eg one providing a full cone spray nozzle or a nozzle providing a hollow cone spray pattern to achieve full coverage with a single spray nozzle. single spray nozzle has a spray angle of 5 degrees SA; The location of the spray nozzle shall be centered at a distance H meters above the casing of the tube with a diameter of D meters according to the formula: / (0/2) = tangent H (5//2) . In the case of a spray nozzle at a distance of JE the spray liquid will not completely cover the tubing. If the spray nozzle is at a greater distance Sige some of the spray liquid against the wall of the aftercooler inlet channel and the spray coverage will not be ideal. oly on the geometry of the abolition aftercooler inlet duct and the abolition downstream pipe; This may be the case that it is difficult to find a suitable single spray nozzle to achieve full coverage

coating for the tubular casing. A complication AT also in selecting a single spray nozzle is that in practice the vapor flow of the quenching stream deflects the spray liquid downward and gives higher flow rates had higher. Therefore, the ideal location for a single spray nozzle can be different for different operating scenarios.

on one side; The condensate of the casing aftercooler can be conveyed to the casing via multiple spray nozzles; For example; Multiple full cone spray nozzles equidistantly located on top of the tubular casing. The spacing between the spray nozzles is such that there is no overlap between the nozzles from adjacent spray nozzles. The angle of the spray nozzles can be selected for the spray covering effect of the tubular casing. For example, the nozzle can be perpendicular to the casing and up to an angle of 60

0 degrees of perpendicularity to the tubular casing. On one side the outlet of the spray nozzles can be between 0.5 Mss and about 1 m from the surface of the tubing; On the AT side from about 0.6 to about 0.9 meters and on the other side from about 0.7 to 0.8 meters. adding a damper on one side; A suppression column aftercooler condensate inhibitor is added before the suppression column aftercooler condensate 5 contacts the tubular jacket. Inhibitors are effective for preventing polymerization. in this aspect; The inhibitor is selected from the group consisting of hydroquinone, methylhydroquinone, and hydroxy-1/10. hydroxy-TEMPO and nitro phenols such as DNBP (2,4-dinitro-6-secondary-butylphenol) and phenylene diamine (2,4-dini 6-sec-butyl phenol), phenylene diamine and mixtures thereof. 0 pH adjustment on one side; The process includes maintaining and optionally adjusting the ideal pH levels of the condensate for the abatement column aftercooler. Maintaining a pH within a specified range provides a low corrosion process and allows for the use of a wider range of building materials in process equipment. in this aspect; The process includes the addition of mild alkylene compounds to the coolant condensate

Subsequent to the quenching column to provide a pH between about 6 and 7. Creons 36 are preferred due to their low cost and ready availability, but alkylene components can also be used, including alkali metal carbonates, alkali earth metal carbonates, bicarbonates, or creons

ammonium carbonate or bicarbonate or carbamate creams or Jie ethylene diamine ethylene diamine propylene diamine hexamethylene diamine and the like and mixtures thereof . on one side; An additive is added to control the pH of the condensate to the aftercooler of the quenching column before the material contacts

0 suppression column aftercooler condenser with suppression column aftercooler. Although the invention disclosed herein is described by means of special embodiments, examples, and applications for it, it shall (Sa) make many changes and modifications thereto by persons with experience in the field without departing from the scope of the invention specified in the claims.

Claims (2)

protection elements 1. Cooling quench effluent process; Operation Jails on: Supplying the quench column flow (70) to the aftercooler of the quench column (80)¢ Cooling the quench effluent (70) to supply condensate to the aftercooler of the damping column quench column (4)85 and recycle at least a portion of the condensate to the quench column aftercooler (85) to the quench column aftercooler (80) at a rate to provide a liquid film thickness between 0.1 and 1.1 mm in the heat exchanger tubes in the -quench column aftercooler 2. The process in accordance with claim 1; Where the quench column flow (70) contains 20 ppm (by weight) or more ammonia and/or 969 by weight or more acrylonitrile 5 3. Process Gd of the protectant 2 where the quench column (70) flow comprises 20 ppm (by weight) or 100 ppm (by weight) ammonia 4 process according to claim 1, wherein an aftercooler condensate inhibitor is added quench column (85) before condensate connection to the aftercooler quench column aftercooler condensate (85) with heat exchanger tubes .heat exchanger tubes 5. Operation Gy of claim 4; Where the recombinant is selected from the group consisting of hydroquinone, methylhydroquinone, 5-hydroxy-TEMPO TEMPO and nitro phenols such as DNBP (4.2-bi). — 7 1 — nitro-6-secondary-butylphenol) and phenylene diamine ‎(2,4-dinitro—6-sec—butyl ‎phenol), phenylene diamine and mixtures thereof. 6. Operation according to claim 1; The condensate is retained for the aftercooler of quench column 5 (85) and optionally adjusted to a pH between 6 and 7. 7. Process in accordance with Claim 6” wherein an additive is added to control the pH of the condensate of the quench column aftercooler (85) before the condensate of the quench column aftercooler contacts the quench column aftercooler Quench column 0 (80). 8. Process dg for claimant 7 where the pH control additive sale is selected from the group consisting of sodium carbonate g alkali metal carbonates 4,318 alkali earth metal carbonates and bicarbonates Bicarbonates, ammonium carbonate, Picronate 636, carbamate creams, Clog ng ethylene diamine, propylene diamine, hexamethylene diamine, and the like, and mixtures thereof. 0 9. Process Bg for claim 1 where the process provides the rate of change of the contamination factor of the tube side in the aftercooler of the quench column (80) in 0.00000478 m2 (degrees) per kilojoule/hour/month (0.00002 m2) (Rusia per kilocalorie/hour/month) or less. 0. Operation Udy of claim 1; Where the process provides a pipe-side contamination factor in the quench column aftercooler 5 (80) 0.0001434 m2 (degrees Lg per kJ/month) 0.0006 m2 (degrees sie) per kcal/h /month) or less. — 8 1 — 1. Operation in accordance with claim 1; The process provides a heat transfer coefficient of 1130 kWh per m2 (°C) (270 kcal/hr per dase or greater). 2. 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